VMS Help DCE_THREADS, Thread Intro, Non Portable Extensions, Thread Attributes Routines  *Conan The Librarian (sorry for the slow response - running on an old VAX)

   pthread_attr_getguardsize_np
                             Obtains the guardsize attribute of the
                             specified thread attributes object.

   pthread_attr_setguardsize_np
                             Changes the guardsize attribute of the
                             specified thread attributes object.